57 research outputs found
VANET Connectivity Analysis
Vehicular Ad Hoc Networks (VANETs) are a peculiar subclass of mobile ad hoc
networks that raise a number of technical challenges, notably from the point of
view of their mobility models. In this paper, we provide a thorough analysis of
the connectivity of such networks by leveraging on well-known results of
percolation theory. By means of simulations, we study the influence of a number
of parameters, including vehicle density, proportion of equipped vehicles, and
radio communication range. We also study the influence of traffic lights and
roadside units. Our results provide insights on the behavior of connectivity.
We believe this paper to be a valuable framework to assess the feasibility and
performance of future applications relying on vehicular connectivity in urban
scenarios
Two-Hop Connectivity to the Roadside in a VANET Under the Random Connection Model
We compute the expected number of cars that have at least one two-hop path to
a fixed roadside unit in a one-dimensional vehicular ad hoc network in which
other cars can be used as relays to reach a roadside unit when they do not have
a reliable direct link. The pairwise channels between cars experience Rayleigh
fading in the random connection model, and so exist, with probability function
of the mutual distance between the cars, or between the cars and the roadside
unit. We derive exact equivalents for this expected number of cars when the car
density tends to zero and to infinity, and determine its behaviour using
an infinite oscillating power series in , which is accurate for all
regimes. We also corroborate those findings to a realistic situation, using
snapshots of actual traffic data. Finally, a normal approximation is discussed
for the probability mass function of the number of cars with a two-hop
connection to the origin. The probability mass function appears to be well
fitted by a Gaussian approximation with mean equal to the expected number of
cars with two hops to the origin.Comment: 21 pages, 7 figure
The Dynamics of Vehicular Networks in Urban Environments
Vehicular Ad hoc NETworks (VANETs) have emerged as a platform to support
intelligent inter-vehicle communication and improve traffic safety and
performance. The road-constrained, high mobility of vehicles, their unbounded
power source, and the emergence of roadside wireless infrastructures make
VANETs a challenging research topic. A key to the development of protocols for
inter-vehicle communication and services lies in the knowledge of the
topological characteristics of the VANET communication graph. This paper
explores the dynamics of VANETs in urban environments and investigates the
impact of these findings in the design of VANET routing protocols. Using both
real and realistic mobility traces, we study the networking shape of VANETs
under different transmission and market penetration ranges. Given that a number
of RSUs have to be deployed for disseminating information to vehicles in an
urban area, we also study their impact on vehicular connectivity. Through
extensive simulations we investigate the performance of VANET routing protocols
by exploiting the knowledge of VANET graphs analysis.Comment: Revised our testbed with even more realistic mobility traces. Used
the location of real Wi-Fi hotspots to simulate RSUs in our study. Used a
larger, real mobility trace set, from taxis in Shanghai. Examine the
implications of our findings in the design of VANET routing protocols by
implementing in ns-3 two routing protocols (GPCR & VADD). Updated the
bibliography section with new research work
Interference-Aware Scheduling for Connectivity in MIMO Ad Hoc Multicast Networks
We consider a multicast scenario involving an ad hoc network of co-channel
MIMO nodes in which a source node attempts to share a streaming message with
all nodes in the network via some pre-defined multi-hop routing tree. The
message is assumed to be broken down into packets, and the transmission is
conducted over multiple frames. Each frame is divided into time slots, and each
link in the routing tree is assigned one time slot in which to transmit its
current packet. We present an algorithm for determining the number of time
slots and the scheduling of the links in these time slots in order to optimize
the connectivity of the network, which we define to be the probability that all
links can achieve the required throughput. In addition to time multiplexing,
the MIMO nodes also employ beamforming to manage interference when links are
simultaneously active, and the beamformers are designed with the maximum
connectivity metric in mind. The effects of outdated channel state information
(CSI) are taken into account in both the scheduling and the beamforming
designs. We also derive bounds on the network connectivity and sum transmit
power in order to illustrate the impact of interference on network performance.
Our simulation results demonstrate that the choice of the number of time slots
is critical in optimizing network performance, and illustrate the significant
advantage provided by multiple antennas in improving network connectivity.Comment: 34 pages, 12 figures, accepted by IEEE Transactions on Vehicular
Technology, Dec. 201
Optimisation of Mobile Communication Networks - OMCO NET
The mini conference âOptimisation of Mobile Communication Networksâ focuses on advanced methods for search and optimisation applied to wireless communication networks. It is sponsored by Research & Enterprise Fund Southampton Solent University.
The conference strives to widen knowledge on advanced search methods capable of optimisation of wireless communications networks. The aim is to provide a forum for exchange of recent knowledge, new ideas and trends in this progressive and challenging area. The conference will popularise new successful approaches on resolving hard tasks such as minimisation of transmit power, cooperative and optimal routing
Connectivity of confined 3D Networks with Anisotropically Radiating Nodes
Nodes in ad hoc networks with randomly oriented directional antenna patterns
typically have fewer short links and more long links which can bridge together
otherwise isolated subnetworks. This network feature is known to improve
overall connectivity in 2D random networks operating at low channel path loss.
To this end, we advance recently established results to obtain analytic
expressions for the mean degree of 3D networks for simple but practical
anisotropic gain profiles, including those of patch, dipole and end-fire array
antennas. Our analysis reveals that for homogeneous systems (i.e. neglecting
boundary effects) directional radiation patterns are superior to the isotropic
case only when the path loss exponent is less than the spatial dimension.
Moreover, we establish that ad hoc networks utilizing directional transmit and
isotropic receive antennas (or vice versa) are always sub-optimally connected
regardless of the environment path loss. We extend our analysis to investigate
boundary effects in inhomogeneous systems, and study the geometrical reasons
why directional radiating nodes are at a disadvantage to isotropic ones.
Finally, we discuss multi-directional gain patterns consisting of many equally
spaced lobes which could be used to mitigate boundary effects and improve
overall network connectivity.Comment: 12 pages, 10 figure
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